I first bought one stick of 512 ram, got three beeps, no video. I
didn't have any other DDR ram around, so I assumed it was because I
needed two sticks (matched pair). I went out and bought another 512
stick that matched. Put them both in space 0 of each channel like it
says. Same problem. Hrmmm. Could it be the video card? Pulled it
out, didn't have any others to test with, same three longs beeps
without the video card in the unit.

Pulled all RAM chips, same long three beeps (I know this isn't telling
me much, but I was reaching for something to be different, a different
beep or some sign of something else, but didn't.

Make sure that the video card and RAM are seated.
You do not need to have 2 sticks of RAM in order for your board to run ...
you only need 2 sticks if youwnat to take advantage of dual channel mode.
If you still get nothing try another video card.

Three long beeps indicates "first 64 KB memory failure." And, I see in
your message that you are trying to use ECC memory. The 865PE chipset,
and of course your D865PERL motherboard, do not support ECC memory. Only
non-ECC memory is supported on this board.